The year I moved, both countries claim me as tax resident — who wins?

The treaty's tie-breaker decides, in strict order: where you have a permanent home available — if both, where your centre of vital interests lies (family, economy, life) — then habitual abode, then citizenship. The risk year is always the moving year: a kept Norwegian home plus family ties can hand Norway the win even after you've physically moved. The fix is evidence, built in advance: housing disposed or rented out long-term, day counts logged, the life demonstrably relocated.